Adds a free-list for physical memory.

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/src/allocators/mod.rs b/kernel/src/allocators/mod.rs
index e69de29..76d85e6 100644
--- a/kernel/src/allocators/mod.rs
+++ b/kernel/src/allocators/mod.rs
@@ -0,0 +1,23 @@
+use core::{ffi::c_void, ops::Range, ptr::addr_of};
+
+pub mod physical_memory_free_list;
+
+/// The number of bits in the offset in a page.
+pub const PAGE_SIZE_BITS: usize = 12;
+
+/// The size of a page, in bytes.
+pub const PAGE_SIZE: usize = 1 << PAGE_SIZE_BITS;
+
+/// Returns the physical address range the kernel is in.
+pub fn kernel_boundaries() -> Range<usize> {
+    extern "C" {
+        static kernel_start: c_void;
+        static kernel_end: c_void;
+    }
+
+    // SAFETY: We only use these as addresses, we never dereference them.
+    let (kernel_start_addr, kernel_end_addr) =
+        unsafe { (addr_of!(kernel_start), addr_of!(kernel_end)) };
+
+    kernel_start_addr as usize..kernel_end_addr as usize
+}